In IC device testers the IC device under test (DUT) is typically inserted in a dedicated socket fixed on a DUT loadboard which is formed with printed circuit leads to the pins of the DUT. Different DUT loadboards with different socket sizes are provided for accommodating the different types of DUT packages to be tested. The different loadboards are interchangeably mounted or installed on pin electronics cards (PEC's) in the test head of the IC device tester. The appropriate loadboard is selected for testing the DUT according to the DUT package style and size.
The pin electronics cards deliver test signals to the respective pins of a DUT mounted on a DUT loadboard and receive resulting pin signals for measurement and testing. These test signals and pin signals must pass through electrical connectors between the PEC's and DUT loadboard. PEC's are typically arranged vertically in a radial array on the "motherboard" of the test head, at least one PEC for each pin of the DUT. The selected DUT loadboard is installed, for example, horizontally on top of the radial array of vertical PEC's.
The electrical connectors are generally secured to the PEC's and join the DUT loadboard to the PEC array. The electrical connectors provide an electrical interface with continuity of test signal and pin signal electrical paths between the PEC's and DUT loadboard for passing test signals and pin signals between the PEC's and the pins of a DUT inserted into the IC device socket on the loadboard. The electrical connectors also provide a physical joinder for mechanically mounting and installing the DUT loadboard on the PEC's. The electrical connectors therefore perform a dual function in providing both an electrical interface and mechanical coupling. They are preferably designed to permit convenient interchangeability of the DUT loadboards.
One type of prior art electrical connector for the DUT loadboard/PEC interface used printed circuit card edge or circuit board edge connectors. Such card edge connectors however are subject to mechanical wear and require excessive mating force to engage the complementary edge connectors.
Another PEC to DUT loadboard electrical connector uses spring loaded contacts at the PEC/DUT loadboard interface. The spring provides both the electrical interface and the mechanical coupling between circuit boards. This system of interconnection provides a mechanical coupling with sufficient mechanical compliance to accommodate relative change of position of the circuit boards due to misalignment and board warpage. An example of such spring loaded contact interconnects are the so called "Pogo" (TM) electrical connectors and contacts manufactured by Augat, Inc., 33 Perry Avenue, Attleboro, Mass. 02703, and used for example, in the MCT 2000 R (TM) series IC device test systems.
A disadvantage of such spring loaded contact electrical interconnects is that the spring is inductive, and the inductance of the spring varies with spring tension and displacement. It is therefore difficult to maintain a constant impedance path for the test signals and pin signals. Undesirable distortion is introduced into the test measurements particularly for high frequency signals characteristic of current high speed ECL devices.
A third type of PEC to DUT loadboard interconnect uses elastomeric conductors or metal layer conductors over elastomeric spacers to provide the electrical interface and electrical connections between the PEC's and DUT loadboard. Such an electrical interconnect maintains substantially constant impedance over the test signal and pin signal electrical paths for measurement of high frequency signals without substantial distortion. A disadvantage of this electrical connector however, is that it affords only limited mechanical compliance and cannot accommodate the relative change of position in the PC boards caused by significant warpage or misalignment.